package org.apache.lucene.index;

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/**
 * Class to write byte streams into slices of shared
 * byte[].  This is used by DocumentsWriter to hold the
 * posting list for many terms in RAM.
 */

final class ByteSliceWriter {

    private byte[] slice;
    private int upto;
    private final ByteBlockPool pool;

    int offset0;

    public ByteSliceWriter(ByteBlockPool pool) {
        this.pool = pool;
    }

    /**
     * Set up the writer to write at address.
     */
    public void init(int address) {
        slice = pool.buffers[address >> DocumentsWriter.BYTE_BLOCK_SHIFT];
        assert slice != null;
        upto = address & DocumentsWriter.BYTE_BLOCK_MASK;
        offset0 = address;
        assert upto < slice.length;
    }

    /** Write byte into byte slice stream */
    public void writeByte(byte b) {
        assert slice != null;
        if (slice[upto] != 0) {
            upto = pool.allocSlice(slice, upto);
            slice = pool.buffer;
            offset0 = pool.byteOffset;
            assert slice != null;
        }
        slice[upto++] = b;
        assert upto != slice.length;
    }

    public void writeBytes(final byte[] b, int offset, final int len) {
        final int offsetEnd = offset + len;
        while (offset < offsetEnd) {
            if (slice[upto] != 0) {
                // End marker
                upto = pool.allocSlice(slice, upto);
                slice = pool.buffer;
                offset0 = pool.byteOffset;
            }

            slice[upto++] = b[offset++];
            assert upto != slice.length;
        }
    }

    public int getAddress() {
        return upto + (offset0 & DocumentsWriter.BYTE_BLOCK_NOT_MASK);
    }

    public void writeVInt(int i) {
        while ((i & ~0x7F) != 0) {
            writeByte((byte) ((i & 0x7f) | 0x80));
            i >>>= 7;
        }
        writeByte((byte) i);
    }
}
